1. The Field of the Invention
The present invention is in the field of thermal insulation materials. More particularly, the present invention relates to portable gas reservoirs and valve mechanism for connecting and/or filling a gas filled thermal insulation material.
2. The Relevant Technology
Thermal insulators have long been important for human survival and comfort in cold climates. The primary function of any thermal insulator is to reduce heat loss (i.e., heat transfer) from a heat source to a cold sink. There are three forms of heat transfer: convection, conduction, and radiation.
Heat loss through convective mixing of gases is caused by the tendency of a gas to form a rotational mixing pattern between a warmed (i.e., less dense) region and a cooler (i.e., more dense) region. In a convection cycle, warmed gas is constantly being exchanged for cooler gas. One of the primary ways in which thermal insulators work is through suppressing convection by trapping or confining a volume of a gas within the insulative material. For example, one of the reasons that a fiber-filled parka feels warm is that the air near the wearer's skin is warmed by body heat and the fibers act to prevent or at least slow convective mixing of the warmed layer of the air with the cold air outside.
Conduction involves heat flow through a material from hot to cold in the form of direct interaction of atoms and molecules. For example, the phenomenon of conduction is one of the reasons why a thin layer of insulation does not insulate as well as a thicker layer.
Radiation involves direct net energy transfer between surfaces at different temperatures in the form of infrared radiation. Radiation is suppressed by using materials that reflect infrared radiation. For example, the glass surface of a vacuum flask is coated with silver to reflect radiation and prevent heat loss through the vacuum region.
Different thermal insulators prevent heat loss through convection, conduction, and radiation in different ways. For example, fiber-based thermal insulators like polyester fiber fill or fiberglass insulation utilize fairly low conductivity fibers in a stack or batt with a volume of air trapped or confined amongst the fibers. Furthermore, conduction is reduced by the random orientation of the fibers across the stack or batt, and radiative heat loss is somewhat reduced because the radiation is scattered as it passes through the fibers.
Another example class of thermal insulators includes closed cell structures, such as foams or microspheres. Closed cell structures are generally comprised of a polymer matrix with many small, mostly closed cavities. As with fiber-based insulations, these insulators conserve heat by trapping a volume of air in and amongst the cells. In fact, convection is effectively eliminated inside the small, closed cells. Furthermore, conduction is reduced by using low conductivity materials, and radiation is low because the cells are typically very small and there is little temperature difference between cavity walls and hence low driving force for radiative heat transfer.
Essentially all thermal insulators present a tradeoff between insulative value (i.e., prevention of convection, conduction, and radiation), bulk, and cost. For example, because of the bulkiness of fiber- or foam-based insulation, achieving a sufficient degree of insulation for a given set of conditions can be difficult without also making the article too bulky for practical use. It should also be appreciated that adding additional fiber- or foam-based insulation inevitably adds weight. Such insulative materials are also static in that the amount of insulative material cannot be changed or adjusted as the user's needs change. For example, if a person is wearing a fiber filled parka or sleeping in a fiber filled sleeping bag, the amount of insulation cannot be increased or decreased as environmental or activity conditions change.
In addition, many typical insulative materials produce toxic and/or environmentally damaging byproducts in the process of manufacture. For example, the manufacturing process for many thermal insulators such as polyester fibers or foams produces CFCs and/or greenhouse gases. Many typical thermal insulators also continue to outgas toxic chemicals long after their manufacture. For example, fiberglass insulation is typically manufactured with formaldehyde compounds that continue to outgas long after the insulation is placed in a wall or other structure. And many typical insulators, such as fiberglass or polyester fiber fill, produce loose fibers that can be harmful if they are inhaled.